This invention relates generally to toilets that can remove waste from a toilet bowl efficiently with small amounts of water.
Water shortages are serious problems in many regions. This had led to government regulation regarding water use efficiency of certain products. For example, some jurisdictions regulate the maximum amount of water used by a toilet during a flush. While usage of as much as 7 gallons per flush was conventional in the early 1950s, current regulations in some jurisdictions require that no more than 1.6 gallons of water be used per flush. There are proposals to reduce the permitted usage further (e.g. to 1.2 gallons/flush).
Even when there is no governmental requirement restricting water usage, environmentally conscious consumers often prefer low water usage toilets. Moreover, water utilities are significantly increasing the cost of water supply, providing yet another motivation for consumers to prefer low water usage toilets.
As water usage per flush cycle is reduced, it is important that cleaning efficiency remain at acceptable levels. If cleaning efficiency is compromised, the consumer will in some situations be led to flush a second time, frustrating the regulatory, conservation, and cost savings goals.
Complicating matters is that in addition to cleaning the bowl sides, the flush water has other functions. It is typically used to form a gravity siphon which helps move the waste out of the bowl. Also, the water is needed to rinse the bowl once the main waste has been dislodged and evacuated. Further, water is needed to re-establish an odor seal in the trap. Also, water needs to be available to clean the entire circumference of the bowl. These additional requirements complicate the design of low water usage toilets.
One way to improve the efficiency of cleaning is to pressurize the cleaning supply of water. However, this can unacceptably increase the cost of the toilet.
Another approach is to split the rim flow into two unequal branches. See e.g. U.S. Pat. Nos. 4,930,167 and 6,397,405. However, prior systems of this type could have evacuation issues at low water usage rates.
Another approach is to use a tapered passage at the bottom of the bowl near the bowl outlet (a/k/a a “jet”) to more efficiently start the siphon out of the bowl. See e.g. U.S. Pat. Nos. 5,218,726, 5,283,913 and 6,145,138. However, achieving adequate cleaning along the sides of the bowl is difficult with low water usage when a substantial portion of the water has been diverted for jet use.
Yet another approach is to use a multi-loop vortex flow approach. See e.g. U.S. patent application publication 2004/0040080. This takes energy out of the water before it reaches the siphon trap, which could be problematic.
In U.S. patent application publication 2003/0115664 there was a toilet disclosed with some rim flow along a right branch, some rim flow along a left branch, and some flow down and straight ahead. However, this design had certain inefficiencies which constrained the reduction in water usage. For example, water entered at a right angle to the rim, thereby dissipating cleaning energy. Further, some water was used in an opposing manner.
It is therefore desired to develop further improved toilets to reduce water usage without undesirably compromising cleaning or other water closet performance characteristics.